Amplitude modulated wave generating circuit for anti-theft car alarm

摘要

The circuit, placed inside the ignition lock of a car (2), includes an oscillating circuit (3) with an aerial (4) and a capacitor (5). A generator (6) supplies a HF oscillation (7) transmitted to a modulator (8) connected to the oscillating circuit. A voltage source (9) supplies both the generator and the modulator. The oscillating circuit generates a HF magnetic field which transmits the modulated oscillation to the key (1) inserted in the lock. The key has an oscillating circuit (10) with a coil (11) and a capacitor (12). A processor (14) in the key receives the modulated oscillation and charges a capacitor (15).